Red macroalgae of the genus Palmaria generally are reddish brown in color with broad, flattened fronds. The fronds arise from a base, usually with a small stipe, and gradually expand to form simple or palmately divided fronds, often with marginal leaflets. The shape of wild type Palmaria fronds can vary from broad ovals to narrow linear segments, though the most common shape is the characteristic palmate form with branching finger-like extensions.
Palmaria palmata, a particular Palmaria species, is a popular ingredient in natural cosmetics and skin care products and also is widely used for food. The species is not particularly palatable when fresh but, if dried carefully and rapidly, is one of the few seaweeds that tastes good. Palmaria palmata is popular in coastal communities of the North Atlantic, particularly Ireland, Scotland, Iceland, Norway, France and Eastern Canada.
Though popular as a human food, Palmaria traditionally has not been used for aquaculture--the agricultural production of marine and freshwater organisms--which is an important and growing industry in the United States. Crustaceans, fish, and shellfish offer a high-protein food source as an alternative to beef, pork, and chicken products. While aquaculture production of crustaceans (such as shrimp and crawfish) or fish (such as baitfish or catfish) is a long-established industry, recent attention has been directed to the aquaculture of abalone.
Abalone is a gastropod, similar to oysters and clams, and is considered a gourmet delicacy. Aquaculture of abalone traditionally has been based on feeding abalone a diet of giant kelp (Macrocystis species) or bull kelp (Nereocystis luetkeana) harvested from wild kelp beds growing naturally in coastal areas. Giant and bull kelps are not an optimal abalone fodder (food source) for aquaculture operations, however. Like most marine algae, such kelps have relatively poor nutritional values and relatively high moisture contents, characteristics which make them poor food sources for abalone. Abalone consuming giant and bull kelps ingest a large amount of water and a low amount of usable food material, and thus exhibit relatively slow growth rates per amount of food consumed. For example, Ebert and Houk reported that bull kelp supports relatively slow abalone growth rates, typically a 30 to 60 .mu.m shell length (SL) increase per day. Abalone Cultivation Methods Used at the California Department of Fish and Game's Marine Resources Laboratory, in HANDBOOK OF CULTURE OF ABALONE AND OTHER MARINE GASTROPODS, 242 (K. Hahn ed., 1989). These growth rate figures were later confirmed by Trevelyan et al., Increasing the yield of red abalone with the alga, Microcladia coulteri, 17 J. SHELLFISH RES. 631 (1998). Slow abalone growth rates and low feeding efficiency (rate of growth per amount of food consumed) of abalone decrease the economic efficiency and profitability of abalone aquaculture operations.
Even though kelps, such as giant and bull kelps, have poor nutritional value for abalone, their abundance in the abalone's natural habitat and the soft texture of their fronds may explain why they have been used as abalone fodder in aquaculture operations. P. E. McShane et al., Factors influencing food selection in the abalone Haliotis rubra (Mollusca: Gastropoda), 176 J. EXP. MAR. BIOL. ECOL. 27 (1994). The abalone aquaculture industry is also located particularly in Pacific coastal areas that support an abundance of giant and bull kelps suitable as abalone fodder. The geographic expansion of the abalone industry is limited to sites where such kelps can be easily harvested in sufficiently large quantities to support land-based and offshore abalone farms. E. E. Ebert, Abalone aquaculture: a North America regional review, in ABALONE OF THE WORLD 570 (S. A. Shepherd et al. eds., 1992). Additionally, governmental regulations and natural events, such as El Nino, affect the use, distribution, and availability of such kelps for harvest. J. P. Mercer et al., General principles of on-shore cultivation of seaweeds: effects of light on production, 221 HYDROBIOLOGIA 125 (1993); S. C. McBride, Current status of abalone aquaculture in the Californias, 17 J. SHELLFISH RES. 593 (1998); Ebert, (1992). For these reasons, the U.S. abalone aquaculture industry historically has been limited to the natural geographical locations of giant kelp (Macrocystis species) or bull kelp (Nereocystis luetkeana), primarily California. If a different food source for abalone were available, abalone aquaculture could spread geographically into other regions.
Moreover, commercial aquaculture operations must consider economic factors and comply with environmental regulations to harvest large quantities of kelp. For example, traditional land-based abalone farms maintain water quality via rapid water volume exchange rates, which flush abalone waste products (e.g. ammonia, nitrates, carbon dioxide, and dissolved organic wastes) from the culture system. These waste products must be processed into more environmentally benign materials to avoid polluting the environment. More environmentally sound aquaculture methods, or improved methods for controlling and processing abalone waste products, would therefore allow aquaculture operations to become more expansive and profitable.